Isosceles triangle 8

If the rate of the sides an isosceles triangle is 7:6:7, find the base angle correct to the nearest degree.

Correct answer:

B =  65 °

Step-by-step explanation:

$$\begin{gathered} a=7 \\ b=6 \\ \cos B=b\mathrm{/}2:a \\ B={\displaystyle \frac{180\mathrm{°}}{\pi }}\cdot \arccos ({\displaystyle \frac{b\mathrm{/}2}{a}})={\displaystyle \frac{180\mathrm{°}}{\pi }}\cdot \arccos ({\displaystyle \frac{6\mathrm{/}2}{7}})=65\text{°}=64\mathrm{°}37^{\mathrm{\prime }}23\mathrm{"} \end{gathered}$$

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